1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device and a cleaning apparatus.
2. Related Art
In manufacturing processes of a semiconductor device, in general, RIE (Reactive Ion Etching) is used as etching for a semiconductor substrate or etching for a structure formed on a semiconductor substrate. When a semiconductor substrate or a structure formed thereon is etched by the RIE, an etching residual material (to be simply referred to as a residual material hereinafter) adheres to the semiconductor substrate or the structure. The residual material is generally called polymer.
In order to remove the residual material, after the RIE step, the semiconductor substrate is exposed to a polymer removal solution. In a conventional technique, in this step, a plurality of semiconductor substrates are processed in units of lots or batches at once. More specifically, regardless of an amount of residual amount adhering to the semiconductor substrate or the like, a plurality of semiconductor substrates are dipped in the polymer removal solution for only a predetermined period of time.
However, when the plurality of semiconductor substrates are processed at once, pattern shapes of the semiconductor substrates or the structures change depending on the amounts of residual material. For example, if an amount of residual material adhering to an insulating interlayer is small, the insulating interlayer may be excessively etched by the polymer removal solution. Due to the excessive etching, an interconnection formed in the insulating interlayer by a damascene method becomes wider than a design width of the interconnection. As a result, the interconnection considerably influences the electric characteristics of the semiconductor device. Furthermore, if amounts of residual material adhering to the insulating interlayer and the bottom of a VIA are large, the residual materials may remain without being completely removed. This causes a defect by a short circuit of the interconnection, a defect by opening the interconnection, or a defect of a VIA contact. As a result, the defects considerably influence the electric characteristics of the semiconductor after all.
In general, as a polymer removal solution, a used solution is circulated for environmental conservation and reduction in cost and recycled. However, when a large number of semiconductor substrates are processed by using the same polymer removal solution, an etching rate varies with an increase in number of semiconductor substrates. This is because a polymer component dissolved from the semiconductor substrate remains in a polymer removal solution to increase the concentration of the polymer component in the removal solution. When the etching rate of the polymer removal solution varies, as described above, the electric characteristics of semiconductor devices are influenced. On the other hand, frequent exchanges of polymer removal solutions may adversely affect the environment and increase the costs (see JP-A H07-193045 (KOKAI)).